1. Field of Invention
This invention relates to a method for removing chromium from a substance, and more particularly to a method comprising the use of ion exchange media to remove hexavalent chromium from water.
2. Description of Related Art
Hexavalent chromium (Cr (VI)) is a hazardous material, which is generated in a number of industrial processes, and can contaminate ground and surface water. A variety of methods for removing hexavalent chromium from water have therefore been developed to prevent or remediate this issue. Perhaps the most prevalent of these is ion exchange.
For example, ion exchange technology has been used for remediation of chromate-contaminated water associated with the former Boomsnub Metal Plating facility in the state of Washington. According to Chmielewski, “Superfund Site Cleanup of Chromate Contaminated Groundwater,” Soil & Groundwater Magazine (December 1999/January 2000), a weak base anion resin, SIR-700, has been used to remove hexavalent chromium from water. According to its manufacturer (ResinTech, Inc. of West Berlin, N.J.), SIR-700 has an epoxy polyamine polymer structure and has optimized capacity when the pH is below 5.
Although SIR-700 has proven to be a valuable means for removing chromate ions from water, the need to reduce the pH below 5 to achieve optimal capacity can add significant operating costs to the remediation process. Moreover, acidified water resulting from the remediation process can also have deleterious environmental effects. For example, there is concern that reintroducing such water to the aquifer surrounding the former plutonium production facility at Hanford, Washington could dissolve radioactive strontium into the groundwater. Neutralizing the water before release adds additional operating costs to the process.
Attempts have been made to overcome the issues associated with low pH processing by processing at a higher pH. However, the results have been less than completely satisfactory. At higher pH levels, unacceptable amounts of chromate leaks through the resin and the throughput of the process is inadequate.
U.S. Pat. No. 8,168,070 B2 purports to provide a strong base ion exchange resin that is more effective for removing chromium from water at neutral and alkaline pH values than at acidic pH values. The improvement is more of a refinement of an existing process offering incremental gains in performance.
Despite the foregoing development, it is desired to provide improved methods and systems for removing chromium from water, which methods and systems address the aforementioned issues associated with pH adjustment.
All references cited herein are incorporated herein by reference in their entireties.